In recent years there has been growing concern and interest over the presence and biological effects of chemical contaminants which are either in water or airborne in the workplace or the home environment. Governmental agencies, employers, and the community at large now recognize the dangers of breathing or ingesting chemical contaminants released into the air and water at home and/or in industry. The dangers and concerns have reached such proportions that governmental agencies such as the FDA, OSHA, and NIOSH now publish lists of chemically hazardous and/or toxic substances and identify the maximum exposure limit considered safe and non-hazardous for each; as well as provide specific methods for the detection and quantitative measurement of these toxic and/or hazardous chemical compositions.
Representative of these dangers and public concerns is the problem regarding ethylene oxide contamination. Ethylene oxide sterilization is used extensively in hospitals and clinical institutions and by many drug and device manufacturers. A recent survey identified 250 services representing 10 billion units per year sterilized by use of ethylene oxide. The utility of this compound for sterilization purposes resides in its inherent toxicity which also makes it imperative that it be handled with extreme care; and that sensible precautions be taken to avoid hazardous or accidental release. OSHA has placed severe limits on the exposure in (parts-per-million) considered safe for persons working with ethylene oxide. Employees working with this toxic compound are typically exposed to traces of ethylene oxide after opening sterilizer doors and upon the degassing of products and packages after sterilization. The ideal method of assessing the risk and the degree of worker exposure is personal monitoring [Romano and Renner, AM. IND. HYG. ASSOC. J. 40;742(1979)].
A variety of other toxic substances have also been identified. The list comprises not only epoxides such as ethylene oxide; but also includes primary and secondary alcohols, glycols, unsaturated olefins of aliphatic and aromatic structure, and the like. A variety of different methods and apparatus have been developed to detect the presence of such chemical compositions and to quantitate their concentration. Of these, the published NIOSH methods remain the standard for this purpose. These methodologies generally, however, are technically difficult, require sophisticated analytical instrumentation, and are cumbersome and time consuming. Some alternatives for monitoring exposure to these chemicals have been developed. These include personal monitoring apparatus involving a variety of different chemical reactions. For example, U.S. Pat. No. 3,714,562 discloses the use of a metallic film to absorb a selected chemical vapor, the presence of the vapor being measured by a change in the resistance of the film. Similar resistance-type systems are described by U.S. Pat. Nos. 3,703,696 and 3,950,980. Another personal detection monitoring system is disclosed by Palmes and Gunnison [American Industrial Hygiene Association Journal 34;78081(1973)]. This described device measures a chemical contaminant as a function of vapor concentration. The process required to identify and/or quantify the vapor exposure within the device requires the sophistication and expense of a well equipped analytical laboratory. More recently, U.S. Pat. No. 4,380,587 describes a film badge for determining carbonyl compounds with a specific direct application to the detection of formaldehyde. This innovation employs the formation and growth of an optically measureable film of crystals to determine the concentration of the carbonyl compound in the test sample. The use of this crystal growing methodology was also employed within the invention of copending application Ser. No. 862,072 filed May 12, 1986, and about to issue as U.S. Pat. No. 4,727,024 on Feb. 23, 1988. The invention described within this patent application employs a prepared conjugate reactant having specific binding properties for an analyte of interest capable of releasing a carbonyl-containing moiety which is subsequently detected by the formation and growth of optically visible crystals.
Despite these recent developments and innovations, there remains a continuing need for methods and apparatus which can detect a variety of different chemical compositions in the air and water. Much of the difficulty in creating a non-instrument, personal monitoring apparatus lies in the fact that non-hazardous and/or toxic substances vary greatly in chemical structure and reactivity; that more than one type of chemical composition is often present in the air or water within the workplace or at home; that the means for detecting each type of hazardous and/or toxic chemical composition is different and frequently unique to that type or class of chemical compound; and that the selectivity and reproducibility of non-instrument methods and apparatus is typically insufficient to detect very low levels of chemical substances and/or to provide accurate and reliable quantitative results. Clearly, therefore, any innovation which improves the sensitivity, reliability, and speed of a non-instrument method and apparatus able to detect a variety of chemically different substances in the ambient environment would be deemed a major advance and long desired achievement in this art.